You are right in your observation. We are really fast in our code analysis and it works as fast as the user types. However it happens that if you type very fast or the analysis feedback comes half a second slower we don't do well. On order to be on the safe side we implemented moving of semi-colon only when we know it's missing at the end of the line (when the analysis send a missing ';' error on the same line). However as it turns out that there are still cases that we don't handle correctly we'll consider improving this behavior and adding some for options for the feature in the next release.
the Telerik team